What causes a crack like this?

[Michael Chambers]

This is a fairly wide (1/4 in. or more in places), horizontal crack running along a garage foundation, about 4 inches down from the foundation top on the exterior side, and as you see it in the photo on the interior side. I see these every once in a while, but don't know what causes them. There is no stress source that I can see, and these cracks don't seem to cause any problems. My neighbor has one just like this in his basement foundation, well above the soil line, and about 6-7 in. down from the foundation top. I'm thinking this may possibly be from bolting down the sill plate too soon, while the concrete is still green, but that's just a WAG (Wild A$$ Guess).

Thanks for the depth of knowledge everyone has, and is so willing to share!

[don agel]

This is a fairly wide (1/4 in. or more in places), horizontal crack running along a garage foundation, about 4 inches down from the foundation top on the exterior side, and as you see it in the photo on the interior side. I see these every once in a while, but don't know what causes them. There is no stress source that I can see, and these cracks don't seem to cause any problems. My neighbor has one just like this in his basement foundation, well above the soil line, and about 6-7 in. down from the foundation top. I'm thinking this may possibly be from bolting down the sill plate too soon, while the concrete is still green, but that's just a WAG (Wild A$$ Guess).

Thanks for the depth of knowledge everyone has, and is so willing to share!

My best guess here would be that the concrete was not properly mixed/cured, or screeted when forming. Would not think that the bolts had anything to do with this as the cracking in the photo shows no sign of bolts anywhere near. What's the deal with the base plate of the framed wall not having pressure treated lumber in direct contact with the concrete?

[Mark Reinmiller]

This is a fairly wide (1/4 in. or more in places), horizontal crack running along a garage foundation, about 4 inches down from the foundation top on the exterior side, and as you see it in the photo on the interior side. I see these every once in a while, but don't know what causes them. There is no stress source that I can see, and these cracks don't seem to cause any problems. My neighbor has one just like this in his basement foundation, well above the soil line, and about 6-7 in. down from the foundation top. I'm thinking this may possibly be from bolting down the sill plate too soon, while the concrete is still green, but that's just a WAG (Wild A$$ Guess).

Thanks for the depth of knowledge everyone has, and is so willing to share!

One possibility is corrosion of rebar. That would assume that there is a horizontal bar near the top of the foundation wall.

[Raymond Wand]

Bad pour into form, concrete was not tamped to remove air pockets.

[Rick Cantrell]

I agree with Don and Raymond. Sorry Mark, I don't think rebar had anything to do with what it shown.

[Mark Reinmiller]

I agree with Don and Raymond. Sorry Mark, I don't think rebar had anything to do with what it shown.

It would not be typical to have rebar near the top of the foundation, but it is sometimes done. As for a bad pour, the only way that would make sense to me is if they poured the forms short and then added more concrete after a delay. Even then, what would account for the separation in the concrete. The cracks are too large for shrinkage cracks and not the right location. Something had to cause the concrete to separate. What I am seeing does not look like honeycombing.

[H.G. Watson, Sr.]

This is a fairly wide (1/4 in. or more in places), horizontal crack running along a garage foundation, about 4 inches down from the foundation top on the exterior side, and as you see it in the photo on the interior side. I see these every once in a while, but don't know what causes them. There is no stress source that I can see, and these cracks don't seem to cause any problems. My neighbor has one just like this in his basement foundation, well above the soil line, and about 6-7 in. down from the foundation top. I'm thinking this may possibly be from bolting down the sill plate too soon, while the concrete is still green, but that's just a WAG (Wild A$$ Guess).Thanks for the depth of knowledge everyone has, and is so willing to share!Hmmm. One bad interior photo of garage floor soft story.Well, gumbo clay, expansive soils, slab shift, the 3 seismic events of note to the general region, see block seams, bad grouting/parging cold joints, overly wetted or old mix for bond beam, failure to water proof the exterior, four flooding events of note to the general region in recent history, freezing following the rain/freezing rain events, sheer tornadic/wind events, a host of "what if" possiblities and no information nor photos of the wall, exterior, grade, information on plumb/level/rack of wall, roof structure, topography, geotechnical survey, etc. Note water staining and apparent white rot.

[Rick Cantrell]

To me it looks as though the concrete was not consolidated.

[Mark Reinmiller]

This is a fairly wide (1/4 in. or more in places), horizontal crack running along a garage foundation, about 4 inches down from the foundation top on the exterior side, and as you see it in the photo on the interior side. I see these every once in a while, but don't know what causes them. There is no stress source that I can see, and these cracks don't seem to cause any problems. My neighbor has one just like this in his basement foundation, well above the soil line, and about 6-7 in. down from the foundation top. I'm thinking this may possibly be from bolting down the sill plate too soon, while the concrete is still green, but that's just a WAG (Wild A$$ Guess).

Thanks for the depth of knowledge everyone has, and is so willing to share!

As is typical with many questions of this type, one closeup photo without any context or other information will get you a lot of guesses, but not many accurate answers.

[Rick Cantrell]

As is typical with many questions of this type, one closeup photo without any context or other information will get you a lot of guesses, but not many accurate answers.
agreed

[Raymond Wand]

If it were honey combing I would expect to see the stones and gaps, not a lateral gaps.

[don agel]

Improper poor as Raymond pointed out and on top of this never kept wet to prevent quick shrinking in Hot dry temperatures.
Curing Concrete | Concrete Technology | Portland Cement Association (PCA) (http://www.cement.org/tech/cct_curing.asp)

:first:

[H.G. Watson, Sr.]

Improper poor as Raymond pointed out and on top of this never kept wet to prevent quick shrinking in Hot dry temperatures.Curing Concrete | Concrete Technology | Portland Cement Association (PCA) (http://www.cement.org/tech/cct_curing.asp)We call that a "cold joint".as in: "...cold joints, overly wetted or old mix..."

[Michael Chambers]

Hmmm. One bad interior photo of garage floor soft story.Well, gumbo clay, expansive soils, slab shift, the 3 seismic events of note to the general region, see block seams, bad grouting/parging cold joints, overly wetted or old mix for bond beam, failure to water proof the exterior, four flooding events of note to the general region in recent history, freezing following the rain/freezing rain events, sheer tornadic/wind events, a host of "what if" possiblities and no information nor photos of the wall, exterior, grade, information on plumb/level/rack of wall, roof structure, topography, geotechnical survey, etc. Note water staining and apparent white rot.

Wow, and I thought I was guilty of a WAG!

Here is a photo of my neighbor's house, showing where the crack is on their foundation. Several years back a foundation repair company talked them into getting it epoxy injected, hence the repair seen here. Basically however, this is the same type of crack I asked about. I've seen this in a number of houses, and have yet to get a good plausible explanation as to what causes this.

If I get a chance to run back by the house I inspected, I'll try to get a photo of that crack's exterior side and post that as well. I thought I had one already, but alas, I don't have it. I'm generally very careful about that.

[Mark Reinmiller]

Wow, and I thought I was guilty of a WAG!

Here is a photo of my neighbor's house, showing where the crack is on their foundation. Several years back a foundation repair company talked them into getting it epoxy injected, hence the repair seen here. Basically however, this is the same type of crack I asked about. I've seen this in a number of houses, and have yet to get a good plausible explanation as to what causes this.

If I get a chance to run back by the house I inspected, I'll try to get a photo of that crack's exterior side and post that as well. I thought I had one already, but alas, I don't have it. I'm generally very careful about that.


When there is concrete above the basement windows there should be rebar above the windows. As I mentioned before that is one possibility. A cold joint could also explain that crack if they poured the top 4-6 inches later. I think the crack in the original photo is too wide to be from a cold joint.

I have been inspecting houses for 28 years and cannot recall seeing cracks like that. Might be some local unique way that they construct concrete foundations.

[Randy Murray]

Looks like it was damaged during backfilling. Probably before it was properly cured.
(first pic.)

[Stuart Brooks]

That is not associated with a "Cold Joint"

Visual Inspection of Concrete - InterNACHI (http://www.nachi.org/visual-inspection-concrete.htm)

Wow! I'm impressed. That is a really good treatise on concrete and cracking. At one time I had to be certified for concrete mix design, materials, placement, and finishing for road and bridge construction. We didn't go into what causes cracks because our job was inspection of the concrete mix, placement, finishing, and curing. Too much water is an automatic concrete killer.

[Frank Bombardiere]

I just had one of those today. At first I thought it was due to rebar rusting and swelling and then I realized there are no rust stains so now I too wonder what it is. Any ideas? One of the pics did not turn out clear, but those are not rust stains at the stem.

[Mike Kleisch]

Another WAG... possible lightening strike for the OP pic.